Pan/Tilt Assembly

[Tanner]

Hi all,

My team is looking at the possibility of making a t-shirt cannon robot over the summer and just for fun we thought of putting the cannon on a pan/tilt module.

We've never done anything like a pan/tilt assembly before. The tilting part is pretty easy for us to figure out from what a few of us figure though the panning part is tripping us up a bit. In 2006, we (or rather last year's graduating class) made a swerve drive using some sprockets mounted onto some wheel 80/20 assemblies. I did some searching on the forums and it appears the same idea/method is plausible. What I wasn't sure of was the alternate methods that could be used.

In other words, what could be used to provide smooth panning-like motion to a t-shirt cannon assembly (probably with some weight to it) with support for an encoder?

Thanks
-Tanner

[sdcantrell56]

mcmaster part number 18635A52

It works amazingly well and isnt too expensive. We used one last year for our turret on our shooter.

[Tanner]

Originally Posted by sdcantrell56

mcmaster part number 18635A52

It works amazingly well and isnt too expensive. We used one last year for our turret on our shooter.

I think we tried using one of those last year for a alternate robot idea. Didn't end up working out too well.

How'd ya'll get it to turn? Sprocket?

Sorry I'm not the mechanically inclined guy on the team.

-Tanner

[nighterfighter]

Originally Posted by Tanner

I think we tried using one of those last year for a alternate robot idea. Didn't end up working out too well.

How'd ya'll get it to turn? Sprocket?

Sorry I'm not the mechanically inclined guy on the team.

-Tanner

If you want, I think we still have part of our T-Shirt bot we made before the season, still assembled.

It had a way to pivot around, and it worked pretty well.
I can see if I can get some pictures.

[kevin.li.rit]

Originally Posted by Tanner

I think we tried using one of those last year for a alternate robot idea. Didn't end up working out too well.

How'd ya'll get it to turn? Sprocket?

Sorry I'm not the mechanically inclined guy on the team.

-Tanner

We used the same thing, we riveted a belt(from the KOP) over the outside of it and attached the pulley onto the globe motor. Worked decent.

[Peter Johnson]

Originally Posted by Tanner

How'd ya'll get it to turn? Sprocket?

We waterjetted a giant aluminum sprocket (LOTS of teeth! ) to bolt onto ours in 2009. Drove with a globe & small sprocket. Worked great, but not for the faint of heart in terms of machining .

[sdcantrell56]

Yeah we also laser cut a ginormous sprocket for ours. We might still have 1 of them laying around if you want it.

[Nathan Streeter]

Our team also used McMaster Part #: 18635A52 for our turreted shooter last year. This bearing worked very well... it was *very* smooth and seemed like it could support far heavier loads than our 20 pound, centrally-mounted shooter!

To control it, we simply used a single rivet to attach a timing belt, and ran the timing belt with a globe motor - we had a push-button limit switch at each extent of the turret's travel, and an encoder on the output shaft of the globe motor. I can't recall the specs on the encoder, and I'm only 80% sure that the encoder was mounted on the output shaft.

Altogether, this set up worked very well for us - it allowed us to autonomously score a couple moon rocks, too!

[kwotremb]

Our team did the same thing as the others last year for our rotateable turret. The turn-table comes with a screw on the side of the turntable, we just cut slits in a timing belt and used that screw to attach the timing belt. Then a globe to rotate with a small gear on it to turn the timing belt.

[billbo911]

In 2009 we built a turret for our robot. It was made from a PVC ring and four V-Channel bearings. It worked flawlessly and still works perfectly today. We will also be modifying it to be our T-Shirt cannon robot. Here are some pictures to help out.



The ring of screws created a sprocket out of the PVC ring so the gates belt could rotate it.



Look closely at the top of this one and you can just see the final product. In this picture the turret is pointed to the right and the motor is visible behind the "C" in "Force".



I'll see if I can get some more detailed picture of the drive mechanism. BTW, we included a pot for position feedback. That allowed us to actually follow another robot and fill 'em up in Autonomous.

[pfreivald]

We used a lazy susan for our 2009 shooter as well -- we rounded a very large ring out of a piece of plywood and then Gorilla glued a timing belt to the outside to turn it into a giant sprocket, then drove it with a timing belt sprocket attached to a globe motor.

It worked *great*, with about 340 degrees of movement before we ran into the edges of the belt -- but that's where we had our limit switches anyway!

An encoder was mounted to the assembly, but we didn't end up using it.

[Zflash]

Originally Posted by billbo911

In 2009 we built a turret for our robot. It was made from a PVC ring and four V-Channel bearings. It worked flawlessly and still works perfectly today. We will also be modifying it to be our T-Shirt cannon robot. Here are some pictures to help out.

1319 did this in 2006 with our pan and tilt turret used for shooting poof balls. The only difference was we used an aluminum ring instead of a PVC one as well as 8 (2 on each corner) V-channel bearings. It certainly does work flawlessly. If you have a copy of the behind the design book our robot is featured in it and I believe has a close up shot. PM me if you want more info or pics.

[Alan Anderson]

The TechnoKats t-shirt cannon was mounted on the team's Rack & Roll practice drivebase for a while. Tilt control was a simple chain and sprocket on the arm's "shoulder" joint. There was no need for a pan mechanism, as the robot itself can turn to face whatever direction is desired.

If we hadn't donated the 2008 Overdrive robot drivebase to our sponsor for target practice, it would have made a fantastic t-shirt cannon platform. Maybe we can mount the remaining superstructure to a simple mecanum drivebase and drive it around that way.

[Andrew Schreiber]

http://www.chiefdelphi.com/media/photos/22693 shows a cad rendering of the 2006 shooter we did on RUSH. Not pictured is the spur gear we had powering it. That can be seen http://www.chiefdelphi.com/media/photos/22666 Here is the whole thing http://www.chiefdelphi.com/media/photos/23193.

We were fortunate to have the water jetting done for us. If you have more questions I will see if I can get someone to either get me some more pictures of it or let me back into the shop so I can snap some of it for you.

[CoachPoore]

Originally Posted by Nathan Streeter

Our team also used McMaster Part #: 18635A52 for our turreted shooter last year. This bearing worked very well... it was *very* smooth and seemed like it could support far heavier loads than our 20 pound, centrally-mounted shooter!

To control it, we simply used a single rivet to attach a timing belt, and ran the timing belt with a globe motor - we had a push-button limit switch at each extent of the turret's travel, and an encoder on the output shaft of the globe motor. I can't recall the specs on the encoder, and I'm only 80% sure that the encoder was mounted on the output shaft.

Altogether, this set up worked very well for us - it allowed us to autonomously score a couple moon rocks, too!

The sensor was indeed mounted on the output shaft of the motor and it was a US Robotics magnetic position sensor. The bearing worked great for us - it even has pre-tapped mounting holes in it.